That’s because there are usually only two paths into federal custody for minors: commit a felony on tribal lands or in Washington, D.C., where the federal government handles prosecutions.

Even the few juveniles who fall into those categories aren’t in actual federal prisons.

Because federal prisons lack programs and services appropriate for young people, juveniles in the federal system are sent to local prisons and jails around the country. One of these is the jail system in the District of Columbia, which holds minors convicted of felonies until they enter the federal prison system at 18. Sylvia Lane, a spokesperson for the district’s corrections department, said there are currently nine such people.

So while there are juveniles in the federal system, the new rules would essentially direct state-level jails and prisons under contract with the feds not to put them in solitary confinement.

Under the rules in place now, these contract facilities are required to notify the federal government when they place juveniles in solitary, and over the course of the last year, they did so 13 times, according to a recently released report on the use of solitary in federal facilities. “Currently, juveniles in federal custody are rarely placed in restrictive housing, and when they are, the placement is typically brief,” the report notes.

Even brief placements for juveniles in the federal system can be grim. In 2013, an ACLU lawyer visited a prison in Deer Lodge, Mont., that contracts with the Bureau of Prisons to hold some of its juvenile prisoners. Juveniles in solitary there were held in 23 hour-a-day lockdown for a minimum of five days in cells with no windows (or frosted windows), with loss of virtually all privileges except access to pencil and paper.

The new rules that Obama announced Monday would only allow such restrictive environments “as a temporary response to a behavioral issue that poses ‘a serious and immediate risk to any individual.’” Advocates describe this as a “cooling off period” measured in minutes or hours, not days. “It’s completely appropriate to put a child in his or her room for a short period of time so they can calm down,” says Mark Soler of the Center for Children’s Law and Policy. “The key is to release these children back into programs and services once they’ve calmed down.”

Given the tiny number of juveniles held in federal prisons, Soler and others hope these changes will send a strong symbolic message to states. “This announcement does not in itself affect a large number of kids, but it’s critically important in raising the issue to a national level and shifting the focus to state systems,” he said.

A Justice Department spokesman, Patrick Rodenbush, say the government has begun the process of modifying contracts with facilities around the country to reflect the new rules.

The president, who is making the new rules through executive action, also prohibited prison staff from punishing low-level infractions by adults with solitary confinement and significantly capped the number of days any prisoner can spend in solitary. These more sweeping changes would affect an estimated 10,000 people a year.